The present invention relates to a display device for displaying lines of text in a character, i.e. word and/or data, processing machine.
German Offenlegungsschrift [Laid-open Application] No. 2,801,750 describes a word processing machine provided with an optical display device on which one complete line of text can be displayed. The operator of such a machine has an opportunity to predetermine the position of the right-hand margin as well as the width of a margin zone which are then displayed on the display device by way of markers. The margin zone is constituted by a selected number of character spaces and the right-hand end of a line of characters within which the line is to terminate as dictated by the line length requirements imposed by the selected text format. When text is put in through the keyboard of the machine, the alphanumeric characters thereof appear on the display device in succession from the left to the right in the sequence in which they were fed in until the marked margin zone is reached. The operator now is able to visually control at which point in the text within the margin zone he wants to initiate a line shift, if necessary after first breaking up a word.
In this known machine the display device must have such a width that a complete line can be displayed because only then can a margin zone be optically marked in advance to then be reached with successive inputs of text. Since, however, the characters on the display device must have a size which makes them satisfactorily legible for the operator, a size which goes considerably beyond the size of the character which will be printed on the record carrier, a display device for a complete line length is too wide to be accommodated in the housing of a conventional office machine. Additionally, the costs for such a multi-position display with associated corresponding multi-position actuating circuits are unjustifiably high for the price level of conventional word processing machines.
In another known word processing machine, described in German Offenlegungsschrift No. 2,742,992, there is therefore provided a display device for displaying part of a line, i.e. always the last 15 characters fed in. The characters which are fed in by means of a keyboard or from a text memory are here displayed on the right-hand side of the display device and, with every input of a new character, are shifted to the left by one position so that in the extreme right-hand position of the text display area of the display device there always appears the character which was fed in last. The operator can preset the desired line length, and a consecutive number display, in a separate area of the display device informs him of the number of spaces in the line already occupied as a result of the actuation of keys. Moreover, the operator has an opportunity to predetermined a margin zone within which he is audibly warned if a space or a hyphen occurs.
With this word processing device there is no expensive and cumbersome whole line display. But since a character display which shifts from the right to the left makes it impossible to optically display, in advance, attainment and, particularly, the width of a margin zone, it is very complicated for the operator to control the right margin. In all cases where there is no hyphen or space in the margin zone, the operator must determine the degree of occupation of the line via the position counter and must calculate the positions, or spaces, in which he has an opportunity to separate a word. The same applies of course for cases in which a line shift is to be made, for example for reasons inherent in the text, not at a hyphen or space accidentally appearing in the margin zone.